The present invention relates to gas discharge displays and, more particularly, is related to methods used to form the final seal in the display device after the insertion of the ionizable gas within the sealed envelope of the display.
The most prevalent prior art approach to forming the final seal in a gas discharge display has been the utilization of a pinched off glass tubulation which projects from the outside surface of one of the insulating plates. This tubulation is utilized to facilitate the evacuation of the atmosphere within the envelope followed by the introduction of the ionizable gas through the same tubulation. Once the envelope receives the ionizable gas, the tube is pinched off to seal the display and retain the ionizable gas within the envelope.
Although this procedure has proved successful with respect to proper evacuation and introduction of ionizable gas into the envelope as well as establishment of an adequate seal, the projecting tubulation presents a fragile protuberance from the display which is exposed to possible breakage during the handling of the display. Quite often displays are damaged as the result of the fragile tubulation being broken or cracked when the displays are being moved or packaged for shipment. The tubulation not only presents a more difficult packaging problem to ensure adequate protection of the tubulation, but also occupies more shipping space.
One prior art arrangement shown in the U.S. Pat. No. 3,914,000 issued to Beckerman et al. shows a method of providing a final seal for a display which does not have a projecting tubulation. However, this particular arrangement requires a specially made type of plug and a small heater for placement closely adjacent the plug to properly melt it. This appears to be a very complicated and unnecessarily time consuming arrangement, since it adds an additional step to the overall process of making the gas display including the formulation of the final seal.
In another prior art device shown in U.S. Pat. No. 4,009,407 issued to Kupsky, a piece of elongated glass rod is positioned adjacent an aperture in the sealing perimeter between the insulating plates. However, there is no disclosure as to exactly how the rod is placed adjacent the aperture in this seal perimeter. No attention is directed to how the seal rod is held in its proper place with respect to a hole in the perimeter of the seal during the sealing process. In certain types of gas discharge displays the perimeter seal is quite narrow, and the use of an edge seal of this type may extend into the viewing window too far.